85, 4.9 l engine shuts down
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New User
Joined: Aug 2002
Posts: 18
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From: Ontario
85, 4.9 l engine shuts down
When the weather is cool and damp, the engine only runs for about one minute then shuts down as if shut off by the ignition. The engine can be started again right away and then shuts down within 30 seconds. This continues untill it warms up then there are no problems. If anyone has any ideas or information it would be most appreciated. Thanks all.
Senior User
Joined: Sep 2002
Posts: 321
Likes: 0
From: kansas
85, 4.9 l engine shuts down
Could be throttle icing.
When air moves from one area to another and the pressure drops so does the temp of the air. Or any gas, this is how air conditioners work. The ac pump creates a high press and low press side. When the freon moves through the orifice from high to low the temp drops damatically.
Getting back to your truck, when cool damp air moves from the outside air pressure, past the throttle blade's narrow opening, the temp drops enough to cause ice crystals to form. As soon as it kills the motor the throttle thaws out. And then you start all over again.
Two things you can check.
First if this occurs at anything other than idle it's something else. This is because you need that narrow opening and large press diff (high vacuum).
Second watch the throttle blade while running. Ice crystals should be evident. Get a buddy to start the truck. You may not be able to get there before it thaws enough you can't see it.
Fixing this is gonna be a problem.
And I don't got a whole lot of suggestions here.
1 Getting truck warmed up quickly may be the best bet.
2 I remember seeing something in Carcraft/Hotrodding magazine about a Redline brand fuel treatment providing enough lubricant to prevent ice from sticking. Run down to the local parts store and look for fuel treatments that claim to lube the valves.
3 Almost every vehicle made anymore has provisions to heat the intake for quick warmup. Usually uses exhaust gas run through the intake. If this is plugged it could aggravate this problem.
Anywho, goodluck and I hope this helps
When air moves from one area to another and the pressure drops so does the temp of the air. Or any gas, this is how air conditioners work. The ac pump creates a high press and low press side. When the freon moves through the orifice from high to low the temp drops damatically.
Getting back to your truck, when cool damp air moves from the outside air pressure, past the throttle blade's narrow opening, the temp drops enough to cause ice crystals to form. As soon as it kills the motor the throttle thaws out. And then you start all over again.
Two things you can check.
First if this occurs at anything other than idle it's something else. This is because you need that narrow opening and large press diff (high vacuum).
Second watch the throttle blade while running. Ice crystals should be evident. Get a buddy to start the truck. You may not be able to get there before it thaws enough you can't see it.
Fixing this is gonna be a problem.
And I don't got a whole lot of suggestions here. 1 Getting truck warmed up quickly may be the best bet.
2 I remember seeing something in Carcraft/Hotrodding magazine about a Redline brand fuel treatment providing enough lubricant to prevent ice from sticking. Run down to the local parts store and look for fuel treatments that claim to lube the valves.
3 Almost every vehicle made anymore has provisions to heat the intake for quick warmup. Usually uses exhaust gas run through the intake. If this is plugged it could aggravate this problem.
Anywho, goodluck and I hope this helps
More Turbo
Joined: Jun 2001
Posts: 572
Likes: 1
85, 4.9 l engine shuts down
I have heard of a cracked or chiped distributor cap causing this problem. if the cap has a crack in it then it will alow moisture inside. this could be why the problem is worst on wet days.
